The invention relates to a damping system for an arrangement between a cylinder head and an injector mounted thereon, particularly in the region of the injector base, as well as to a damping element for an arrangement between the cylinder head and the injector mounted thereon, particularly in the region of the injector base.
In the case of internal-combustion engines having a crankcase, a cylinder head and a combustion chamber, fuel is normally injected into the combustion chamber by means of an injector. For this purpose, the cylinder head of the internal-combustion engine has a dome, which leads into the combustion chamber and in which the injector is accommodated. During the intermittent injection in the operation of the internal-combustion engine, strong vibrations, which have a negative effect on comfort and acoustics, are generated as a result of the opening and closing of the injector valve. Particularly at increased fuel pressures, as may prevail in direct-injection systems of Otto and diesel engines, the vibration-caused stress is intensified. Furthermore, modern combustion methods, in which multiple injection takes place during the intake and compression stroke, especially contribute to the undesirable development of noise and vibrations.
For reducing the noise emission, it had been suggested to brace the injector mounted on the cylinder head and to arrange a damping element at the connection point between the cylinder head and the injector. This type of an arrangement having a damping element is known from German Patent document DE 101 26 336 A1, where it is suggested to use graphite, a plastic material, or a memory metal as the material for the damping element. In this case, the known damping element is constructed in one piece.
In order to achieve a high damping effect, it is necessary in this case that a sufficient quantity of damping material be arranged between the injector and the cylinder head and that the damping element be designed to be correspondingly voluminous. In this case, it was found to be disadvantageous that an exact positioning of the injector with respect to the cylinder head and thus of the injection point in the combustion chamber cannot always be achieved. In particular, because of high dimensional tolerances and an elastic or plastic deformation of the damping element, the injector and, therefore, the injection point may be displaced over time, so that the operation of the internal-combustion engine is impaired.
It is therefore an object of the invention to improve up the above-mentioned damping system or damping element such that, in addition to an effective damping and an uncoupling of the injector from the cylinder head, low dimensional tolerances and a precisely positioned fixing of the injector with respect to the cylinder head are also achieved. In addition, an elastic and/or a plastic deformation of the damping element over its service life should be avoided.
This object is achieved by providing a damping system having a multipart construction. The multipart construction permits the integration of further functions, in addition to the damping, in the damping system. Another solution of the same task is obtained by providing a damping element made of a metal cushion.
Particularly advantageous developments and further developments of the invention are described and claimed herein.
It is preferable for the damping system to have a first partial function area, which is essentially suitable for the damping, and a second partial function area, which is essentially suitable for the precisely positioned fixing.
The first partial function area expediently includes an element that dampens based on the characteristic of its material and/or its design. In this case, it was found to be advantageous to use a metal cushion made of a wire mesh which, as required, contains coated wires and/or synthetic fibers. In addition to the material used, the special damping characteristic is also the result of the special design and/or the construction of the first partial function area. A very high energy dissipation takes place in the metal cushion made of wire mesh as a result of the friction between the wires. The degree of damping can still be increased by coating the wire and/or interwoven synthetic fibers. In connection with the good damping characteristic, the mechanical dimensional stability of the metal cushion is particularly advantageous.
It is very advantageous for the first partial function area to be further developed in a ring-shaped fashion, having at least approximately a rectangular or square cross-section.
The second partial function area preferably includes a first injector-side part as well as a second cylinder-head-side part, the first and the second part of the second partial function area being mutually connected by way of the first partial function area. In this context, the uncoupling from the first and the second part of the second partial function area is essential.
Expediently, the first part of the second partial function area is further developed as an inner ring reaching around the first partial function area on the interior side and the injector side, and the second part of the second partial function area is further developed as an outer ring surrounding the first partial function area on the outer side and the cylinder head side. Because of its bowl-type further development, the second part of the second partial function area is suitable for collecting, for example, abraded particles from the metal cushion made of a wire mesh or other particles, so that such particles are advantageously prevented from entering into the combustion chamber. In that the second part of the second partial function area is arranged between the cylinder head and the first partial function area, wear at the cylinder head as a result of abrasion is avoided and the damping effect is simultaneously increased.
It is advantageous for the first and the second part of the second partial area to be connected with the first partial function area by way of a clamp fit.
In the case of the damping element according to the invention, the metal cushion preferably consists of a wire mesh or of a metal foam. A further improvement of the damping characteristic can be achieved in that the metal cushion includes coated wires, synthetic fibers, and/or graphite.
The metal cushion expediently has a ring-shaped design, having an at least approximately rectangular or square cross-section so that, particularly in connection with the selected material of the damping element, a particularly high positioning and measuring accuracy is achieved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.